How to scale unconnected edges using individual origins in python?
You might do something like:

import bpy
import bmesh

obj = bpy.context.edit_object
bm = bmesh.from_edit_mesh(obj.data)

# current selection
edges = [e for e in bm.edges if e.select]

for e in edges:
    v1 = e.verts[0].co
    v2 = e.verts[1].co
    origin = (v1+v2) * 0.5  # edge origin
    bmv1 = bm.verts.new(((v1-origin) * 2) + origin)
    bmv2 = bm.verts.new(((v2-origin) * 2) + origin)
    bme = bm.edges.new([bmv1, bmv2])

bmesh.update_edit_mesh(obj.data, True)


I may be mistaken but I don't think at present the pivot point has any influence on bmesh.ops. So a slight modification of your original code gives a matrix to each new edge to scale: https://gist.github.com/zeffii/71862f5b1cad1bf1d2c1